Examples of piezoelectric resonators currently used include crystal oscillators and crystal resonators. With this type of piezoelectric resonator, the casing is made up of a rectangular parallelepiped package. This package is constituted by a base and a lid, and a piezoelectric resonator plate is held on and joined to the base with a conductive adhesive made of a flowable material in the interior of the package. The piezoelectric resonator plate is hermetically sealed in the interior of the package by joining the base and the lid (see Patent Document below, for example).
With the technique of Patent Document 1 below, the piezoelectric resonator plate is joined to the base with a conductive adhesive. At the time of this joining, external stress from the conductive adhesive (joint stress occurring in the case of joining the piezoelectric resonator plate to the base) is directly applied to the piezoelectric resonator plate and adversely affects the characteristics of the piezoelectric resonator plate (such as frequency).
Also, with the technique of Patent Document 1 below, electrodes of different polarities are arranged on the base and each is coated with a conductive adhesive, and using this conductive adhesive, the piezoelectric resonator plate is joined to the base. This conductive adhesive is made of a flowable material and thus spreads (flows) over the substrate when applied on the electrodes or when used for joining the piezoelectric resonator plate to the base, thereby causing a short between the electrodes of different polarities.